iPhone：如何将带有货币符号的字符串转换为负数？

Question

假设我有一个 23.56 英镑或 23.56 美元的字符串，如何将其转换为 -23.56？

我有这部分

NSMutableString *strAmount = [NSMutableString stringWithString:txtAmount.text];
[strAmount replaceCharactersInRange: [strAmount rangeOfString: strCurrencySymbol]  withString:@""];

Answer 1

这看起来是一个好的开始。您可以使用 rangeOfCharacterFromSet: 而不是 rangeOfString: 尽管在创建一组货币符号之后。您的代码可能如下所示：

NSMutableString *strAmount = [NSMutableString stringWithString:txtAmount.text];
NSCharacterSet *currencySet = [NSCharacterSet characterSetWithCharactersInString:@"$€£"];
[strAmount replaceCharactersInRange: [strAmount rangeOfCharacterFromSet:currencySet]  withString:@"-"];

Answer 2

使用NSNumberFormatter

NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setNumberStyle:NSNumberFormatterCurrencyStyle];
[formatter setLenient:YES];

NSNumber *number = [formatter numberFromString:@"£23.56"];

NSDecimalNumber *minusOne = [NSDecimalNumber decimalNumberWithString:@"-1.00"];
NSDecimalNumber *money = [NSDecimalNumber decimalNumberWithDecimal:[number decimalValue]];
NSDecimalNumber *negativeMoney = [money decimalNumberByMultiplyingBy:minusOne];

NSLog(@"£23.56 is now %@", [negativeMoney description]);